The mean (SD) percentage of GSTO1-1 positive macrophages in non-smokers was 40 (30), smokers 19 (25), COPD stage I-II 24 (26) and COPD stage IV 58 (36) and the mean difference was significant at 0.05 level between stage IV COPD and smokers and between stage IV and stage I-II COPD (Figure 2B). Here, GSTO1 is linked to chronic obstructive pulmonary disease.